Rotary switch having improved crosstalk and matching characteristics



Dec. 10, 1963 c. w. CONCELMAN 3,114,118

ROTARY SWITCH HAVING IMPROVED CROSS-TALK AND MATCHING CHARACTERISTICS Filed Nov. 21. 1960 f INVENTOR 67444 M dawn/.010

BY/M

7ATTORNEY United States Patent Office 3,114,118 ROTARY SWITCH HAVING IMPROVED CROSS- TALK AND MATCHlNG CHARACTERISTHCS Carl W. Concelman, Danhnry, Conn., assignor to Amphenol-Borg Electronics Corporation, Broadview, 111., a corporation of Delaware Filed Nov. 21, 1938, Ser. No. 76,661 3 Claims. (Cl. 333-7) The present invention relates to high frequency coaxial electrical switches for selectively connecting a first high frequency coaxial transmission line to individual ones of a pair of such lines and, in particular, concerns a rotary switch of the type shown in U .8. Patent 2,640,115.

It is a principal object of the present invention to improve the electrical characteristics of a coaxial switch of the general type shown in U.S. Patent 2,640,115 with respect to its crosstalk and impedance matching characteristics without any substantial increase in the complexity of the switch as to its fabrication or use.

It is a further object of the invention to provide a shield element in a rotary coaxial switch of the type contemplated herein, which switch employs an enclosed chamber into which an axial inner conductor and a pair of radially spaced inner conductors extend. The switch also employs a radial switch arm at all times connected to the axial inner conductor and alternate ones of the radial inner conductors to effect alternate switching operation. The improved cross-talk and matching characteristics are effected by the shield element suitably supported in the chamber between the inner conductors and which element is provided with a longitudinal slot to clear the switch arm for movement.

Further objects and advantages will become apparent from the following description of the invention taken in conjunction with the figures, in which:

FIG. 1 is an exploded elevational view partly in section of a switch employing the principles of the instant invention;

FIG. 2 is an end view in elevation of a portion of the assembled switch taken along line 2-2 of FIG. 1; and

FIG. 3 is an exploded view in perspective of the shielding element employed in the switch chamber in accordance with the principles of the invention.

Reference is now made to the figures for an illustration of a switch 10 incorporating the principles of the invention. Switch 10 involves a solenoid motor 11 for actuating switching operation. Switch 10 includes a support or body comprising a cup shaped housing 12 having a stepped axial bore 13 in which a notched member 14 is seated upon assembly of switch 10. The left side of housing 12 is enclosed by an end wall 15 and the opposite and open end of bore 13 is enclosed by an end wall 16 provided by a cylindrical cover 17. These elements, housing 12, notched member 14 and cover 17, are all constructed of suitable electrically conductive material, such as brass, which is in accordance with the usual practice silver plated. Housing 12 has a flange 18 at the mouth of bore 13 for supporting bolts 19', which bolts pass through member 14, cover 17 and are threadedly attached to solenoid motor 11, whereby these elements are held together in assembly. Notched member 14 is essentially a cylindrical disc with a V-shaped undercut or notch. The notch is defined by opposed first and second walls 2%, 21 joined by an arcuate wall portion 22. When the foregoing elements are assembled and attached, the first and second walls 20, 21 and the opposed parallel spaced end walls 15, 16 in cooperation with the portion of the interior peripheral wall 23 of housing bore 13 bridging the open notch define an enclosed switching chamber 24. As seen from the figures, upon assembly of switch 10, member 14 nests in the small diameter section of axial bore \13 3,114,118 Patented Dec. 10, 1963 whereby the opposite faces 25, 26 of member 14 are contiguous with the individual end walls 15, 16; walls 20, 21 and 22 extend orthogonal from end wall 15 to end Wall 16. p

A first electromagnetic wave energy coaxial connector 27 is supported by housing end wall 15 for connection with a coaxial transmission line. Connector 27 has an outer conductor 28 and an inner conductor 29 suitably supported by insulating means 36 within outer conductor 28. Connector 27 extends along the horizontal center line of axial bore 13 and its inner conductor 29 terminates with a rounded smooth end in chamber 13. A pair of electromagnetic wave coaxial connectors 30,. 31 are adapted for connection with individual ones of a pair of coaxial transmission lines. Each connector 30, 31 has a respective outer conductor 32, 33 supported by the peripheral wall of housing 12 and a respective inner conductor 34, 35 supported coaxially by insulating means 36 in outer conductors 32, 33. Inner conductors 34, 35 extend into chamber 13 from the portion of peripheral wall 23 bridging chamber 24 and terminate in chamber 24. Inner conductors 34, 35 extend along radially spaced axes into chamber 24 with a minimum of penetration but suflicient to make conductive cont-act with a switch arm 37 to effect switching operation. The outer ends of connectors 27, 3t}, 31 are provided with suitable fittings to make connection with the individual transmission lines (not shown herein).

Although connectors 30, 31 are radially spaced apart the radial axes thereof and in particular, the portions of the inner conductors 34, 35 in chamber 24 are coplanar. it is also seen that inner conductor 34 is adjacent chamber wall 29, that inner conductor 35 is adjacent chamber wall 21 and that inner conductor 29 is adjacent arcuate chamber wall 22. The walls of chamber 2.4, specifically walls 21 21, 22, are effectively tangential to the individual adjacent outer conductors. By effectively tangential, .it is meant that the chamber walls 20, 21, 22 lie'in planes which are substantially tangent to contiguous sections of the outer conductors of the individual adjacent connectors. Wall 23 in turn is relatively circumferential and bridges chamber 24 to extend between walls 26 and 21. Moreover, chamber walls 20, 21, 22 have an axial dimension a normal to the plane of the radial axes of inner conductors 34, 35. Dimension a is approximately equal to the diameter of outer conductors 32, 33. Upon assembly of switch 14), it will be understood that the chamber walls and the three outer conductors are electrically common.

Cover 17 has a cylindrical projection 38 wherein the inner face thereof defines chamber wall 16. Upon assembly of switch 10, projection 38 nests in the larger diameter section of bore 13. Projection 38 has an axial opening 33 for supporting a bearing member 41 Bearing member 43 carries an insulator 41 to turn therewith, which insulator 14 has an oil-set end. The axially thin resilientradial switch arm 37 is carried by insulator 41 to turn therewith. Arm 37 is electrically isolated from the chamber walls by insulator 41. Upon assembly of switch 10, switch arm 37 is supported in chamber, so that its lower portion is at all times in conductive contact against the rounded end of inner conductor 29. Switch arm 37 bridges the distance between inner conductor 29 and inner conductors 34, 35, whereby the upper portion ofswitch arm 37 extends radially to permit conductive connection with the sides of individual ones-of inner conductors 34, 35. The upper end of arm 37 terminates within chamber 24 to avoid contact with chamber wall 23.

Movement of switch arm 37 from one to another of its two make contact positions about the axis of conductor 29 is effected by any well known device, such as solenoid motor 11. Solenoid 11 includes a rotatable shaft 42 having a radial key or pin 43. Upon assembly of switch 10, pin 43 registers with a keyway 44 at the adjacent end of bearing member 40 to turn same. A fiat coil spring 45 is operatively attached to shaft 42. Spring 45 is mounted on solenoid 11 by clamp means 46. Shaft 42 is held in one rotatable position when solenoid 11 is de-energized whereby bearing member 40 is correspondingly positioned. This holds switch arm 37 in a first of its make contact positions, for example, as shown in FIG. 2, wherein its upper end is in contact with conductor 34 to couple the transmission lines connected to connectors 27, 30 together through switch 19. In this condition, connector 31 is inactive. Solenoid 11 may be energized by the application of suitable voltage potential to a pair of input terminals 47 and when energized causes shaft 42 to turn, whereby switch arm turns therewith to its second make contact position. Arm 37 now contacts conductor 35 to couple the transmission lines connected to connector 27, 31 whereas connector 30 is inactive. When solenoid 11 is again deenergized, spring 45 returns switch arm to the first make contact position. If desired, solenoid 11 may also include additional internal stop means to prevent switch arm from swinging beyond either of the make contact positions to avoid contact with walls 20, 21. Key 43 and the adjacent elements of solenoid 11, such as, spring 45 and clamp means 46, nest in bore 48 of cover 17 upon assembly of switch 10. The description of the rocking device or means for pivoting switch arm 37 from one to the other of its make contact positions, is briefly described herein because it is not an element of the claimed improvements. It will be understood that other well known operating devices or manual operations may be used to alternate switch arm 37 from one to the other of its two make contact positions.

The principal of the invention involves supporting shield element means 49 in chamber 24. Shield means is illustrated in the figures as a pair of arcuate shield bodies 50, 51 made of electrically conducting material. Shield bodies 50, 51 have an axial width substantially equal to a. One end of each shield body is embedded in an individual chamber wall 20, 21 and soldered thereat to hold firmly the composite shield element 49 in desired position in chamber 24. Shield element 49 is substantially symmetrical with respect to the vertical radius as viewed in FIG. 2 upon assembly of bodies 50, 51 in chamber 24. In the elevational view of FIG. 2, the arcuate wall 49a defined by shield 49 lies in a circumferential plane substantially parallel to peripheral wall 23. Each shield body 50, 51 has a turned end 491) forming contiguous portions extending radially towards chamber wall 23. The upper edges of turned ends 4% need not actually touch wall 23, but terminate close to wall 23. It will be noted that the circumferential plane 49a of shield 49 extends between Wall 23 and conductor 29 and, in particular, above conductor 29 and below the ends of conductors 34, 35 to electrically shield the latter pair of conductors from conductor 29. The upturned shield ends 4% extend radially between walls 20, 21 and, in particular, mid-way between conductors 34, 35 so that essentially three component chambers are defined by shield 49, each for an individual one of the three inner conductors extending into chamber 24. Each shield body 50, 51 has an off-set slot 52 and upon assembly in chamber 24 the slots are aligned to form a circumferential clearance 52 through which switch arm 37 passes, whereby arm 37 is cleared for movement from one to the other of its two make contact positions.

Shield 49 serves two purposes. First, it eifectively electrically shields the inactive inner conductor and thus its circuit from the active inner conductors, that is to say, it improves the cross-talk characteristics between the inactive circuit and the connected circuits. In addition, shield 49 capacitively loads chamber 24 which improves the impedance match with the coaxial cables connected to switch 10. As understood in the art, crosstalk means picking up a signal in the inactive circuit which may be opened, grounded or resistor terminated as a result of a relatively imperfect isolation of such inactive circuit from the active circuits. With respect to the operation of switch 10, it will be understood that the circumferential width b of switch arm 37 is less than the circumferential separation of shield portion 491) from walls 20, 21, respectively. Accordingly, when arm 37 is in its first make contact position as shown in FIG. 2, no part of arm 37 above the arcuate portion 49a of shield 49 reaches into chamber portion 24b surrounding inactive conductor 35. In this position, the upper part of arm 37 is contained within chamber portion 24a surrounding the connected conductor 34. A reverse relationship exists when arm 37 is in its other make contact position, at which time the chamber portion 24a surrounding inactive conductor 34 does not contain any part of switch arm 37.

In order that electromagnetic wave energy propagate well in a coaxial transmission line, it should be characterized by a uniform capacitance and inductance per unit length. Consequently, under ideal conditions, switch 10 should have the same impedance per unit length as the cables to which switch 10 is attached. Switch 10 upon assembly will have a certain impedance between the inner conductor paths, for example conductors 29, 37 and 34 or 35, and the outer conductor paths, for example 28, the chamber walls and 32 or 33. Without the use of shield 49, a relatively large gap exists between switch arm 37 and the outer conductor path in switch 10, such as wall 15, whereby the capacitance of switch 10 is relatively low. The insertion of shield 49 is designed to increase the capacitance per unit length of switch 10 to improve its matching characteristics, whereby switch 10 exhibits a better match with a 50 ohm line.

The slot dimension S (FIG. 3) plays a part in controlling the amount of shielding and also switch impedance. The shield effect is increased and capacitance of switch It) is increasedby making slot dimension S smaller, although it will be understood that this dimension must always be wide enough to pass switch arm 37 without contacting shield 43 to avoid shorting of arm 37. In addition, the shield dimension d, that is to say, the separation of its arcuate plane 49a from wall 23, may be increased to increase the capacitance of switch 10. Moreover, the thickness of the shield dimension t, if increased, will increase the capacitance between shield 43 and arm 37 and, hence will increase the capacitance of switch 10. By selecting suitable dimensions for S, d and t, an impedance per unit-length for switch 10 may be established to effect improved impedance matching with the coaxial cables connected to switch 10. With respect to a switch employing the principles of the invention, it was found that upon terminating connector 27 with a 50 ohm line and both connectors 30, 31 are terminated with match loads, switch 10 provides an impedance match with the VSWR less than 1.2 from- 0-1000 me. when switch arm 37 is in either of its make contact positions. Cross-talk to a terminated connector 31 is better than db down when switch was in either of its make contact positions with the signal applied to connector 39 and connector 27 terminated with a matched load.

In one embodiment, shield bodies 59, 51 were shaped from blanks of spring phosphorous bronze and formed to provide an arcuate plane 49a having a radius of about .328 inch for mounting in a chamber 24 having a radius of about .469 inch. The blank material was selected to provide a shield thickness 1 of about .015 inch and was provided with a dimension 8 of about .062 inch for slot 52 to pass a switch arm 37 having a thickness of abou .004 inch.

It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electrical switch for selectively connecting a first electromagnetic wave transmission line to individual ones of a pair of such lines, wherein said switch including a conductive body having an internal chamber defined by first and second opposed conductive walls joined at an apex at one end and being bridged by a peripheral conductive wall at an opposite end, said chamber also including a pair of parallel spaced conductive end walls, said first and second walls extending in respective planes orthogonal to said parallel end walls, a first coaxial connector for connection to the first transmission line and having an inner conductor extending into said chamber adjacent the chamber apex and along an axis normal to said parallel end walls, a pair of coaxial connectors for individual connection with said pair of transmission lines and having respective inner conductors extending radially into said chamber from said peripheral wall and between said first and second opposed walls, movable conductive switch means supported in said chamber for connecting said first inner conductor with alternate ones of said pair of inner conductors in response to switching movement from one to another of two positions, the combination comprising, an arcuate conductive shield element supported in stationary relationship in said chamber and making conductive connection with said chamber walls, said shield bridging the distance between said first and second opposed Walls and lying in an arcuate plane uniformly spaced from said peripheral wall, the plane of said shield being located between said peripheral wall and first inner conductor, said pair of inner conductors projecting wholly in the chamber space between said peripheral wall and said shield, said shield having a turned portion extending radially towards said peripheral wall and between individual ones of said pair of inner conductors so as to shield one electrically from the other, said shield having an arcuate slot of preselected width through which said switch means extend for Clearing said switch means for movement from one to another of its two switching positions, the width dimension of said slot coextending in the same direction as the width dimension separating said parallel end walls, the degree of electrical shielding and effective capacitance of said chamber being a function of the size of said slot Width, movement of said switch means to one or the other of its two switching positions effects the electrical connection between said first inner conductor and an individual one of said pair of inner conductors, whereas the other of said pair of inner conductors is inactive and electrically shielded from the connected inner conductors.

2. Apparatus as defined in claim 1, wherein one inner conductor of said pair is adjacent to said first wall and the other inner conductor of said pair is adjacent said ccond wall, the size or" said switch means being less than the se aration between the turned portion of said shield and said first and second walls, said switch means being confined entirely between said turned portion and the respective ones of said first and second walls when said switch means is in one or the other of its two positions.

3. Apparatus as defined in claim 2 wherein the eiiective capacitance of said switch is also a function of the distance between the plane of said shield and said peripheral wall and the radial thickness of said shield.

References Cited in the file of this patent UNITED STATES PATENTS 2,640,115 Concelman May 26, 1953 2,816,198 Cherry Dec. 10, 1957 FOREIGN PATENTS 646,510 Great Britain Nov. 22, 1950 

1. IN AN ELECTRICAL SWITCH FOR SELECTIVELY CONNECTING A FIRST ELECTROMAGNETIC WAVE TRANSMISSION LINE TO INDIVIDUAL ONES OF A PAIR OF SUCH LINES, WHEREIN SAID SWITCH INCLUDING A CONDUCTIVE BODY HAVING AN INTERNAL CHAMBER DEFINED BY FIRST AND SECOND OPPOSED CONDUCTIVE WALLS JOINED AT AN APEX AT ONE END AND BEING BRIDGED BY A PERIPHERAL CONDUCTIVE WALL AT AN OPPOSITE END, SAID CHAMBER ALSO INCLUDING A PAIR OF PARALLEL SPACED CONDUCTIVE END WALLS, SAID FIRST AND SECOND WALLS EXTENDING IN RESPECTIVE PLANES ORTHOGONAL TO SAID PARALLEL END WALLS, A FIRST COAXIAL CONNECTOR FOR CONNECTION TO THE FIRST TRANSMISSION LINE AND HAVING AN INNER CONDUCTOR EXTENDING INTO SAID CHAMBER ADJACENT THE CHAMBER APEX AND ALONG AN AXIS NORMAL TO SAID PARALLEL END WALLS, A PAIR OF COAXIAL CONNECTORS FOR INDIVIDUAL CONNECTION WITH SAID PAIR OF TRANSMISSION LINES AND HAVING RESPECTIVE INNER CONDUCTORS EXTENDING RADIALLY INTO SAID CHAMBER FROM SAID PERIPHERAL WALL AND BETWEEN SAID FIRST AND SECOND OPPOSED WALLS, MOVABLE CONDUCTIVE SWITCH MEANS SUPPORTED IN SAID CHAMBER FOR CONNECTING SAID FIRST INNER CONDUCTOR WITH ALTERNATE ONES OF SAID PAIR OF INNER CONDUCTORS IN RESPONSE TO SWITCHING MOVEMENT FROM ONE TO ANOTHER OF TWO POSITIONS, THE COMBINATION COMPRISING, AN ARCUATE CONDUCTIVE SHIELD ELEMENT SUPPORTED IN STATIONARY RELATIONSHIP IN SAID CHAMBER AND MAKING CONDUCTIVE CONNECTION WITH SAID CHAMBER WALLS, SAID SHIELD BRIDGING THE DISTANCE BETWEEN SAID FIRST AND SECOND OPPOSED WALLS AND LYING IN AN ARCUATE PLANE UNIFORMLY SPACED FROM SAID PERIPHERAL WALL, THE PLANE OF SAID SHIELD BEING LOCATED BETWEEN SAID PERIPHERAL WALL AND FIRST INNER CONDUCTOR, SAID PAIR OF INNER CONDUCTORS PROJECTING WHOLLY IN THE CHAMBER SPACE BETWEEN SAID PERIPHERAL WALL AND SAID SHIELD, SAID SHIELD HAVING A TURNED PORTION EXTENDING RADIALLY TOWARDS SAID PERIPHERAL WALL AND BETWEEN INDIVIDUAL ONES OF SAID PAIR OF INNER CONDUCTORS SO AS TO SHIELD ONE ELECTRICALLY FROM THE OTHER, SAID SHIELD HAVING AN ARCUATE SLOT OF PRESELECTED WIDTH THROUGH WHICH SAID SWITCH MEANS EXTEND FOR CLEARING SAID SWITCH MEANS FOR MOVEMENT FROM ONE TO ANOTHER OF ITS TWO SWITCHING POSITIONS, THE WIDTH DIMENSION OF SAID SLOT COEXTENDING IN THE SAME DIRECTION AS THE WIDTH DIMENSION SEPARATING SAID PARALLEL END WALLS, THE DEGREE OF ELECTRICAL SHIELDING AND EFFECTIVE CAPACITANCE OF SAID CHAMBER BEING A FUNCTION OF THE SIZE OF SAID SLOT WIDTH, MOVEMENT OF SAID SWITCH MEANS TO ONE OR THE OTHER OF ITS TWO SWITCHING POSITIONS EFFECTS THE ELECTRICAL CONNECTION BETWEEN SAID FIRST INNER CONDUCTOR AND AN INDIVIDUAL ONE OF SAID PAIR OF INNER CONDUCTORS, WHEREAS THE OTHER OF SAID PAIR OF INNER CONDUCTORS IS INACTIVE AND ELECTRICALLY SHIELDED FROM THE CONNECTED INNER CONDUCTORS. 